Planet 7 Casino - Unfairly voided winnings

I was playing in planet 7 casino when I first started I took a survey 20 coupon for a free $20 to play. I was told I had to play out the 20 before I could add more funds otherwise it would be considered mixing of funds which would void any winnings. I played out the 20 to zero then I added my own money via neteller, and never took any other bonuses from them. Over time I eventually won over $1000. I decided I was going to withdraw $1000 . I submitted all required documents and waited. After about 2 weeks or so I happened to log in only to see my balance at zero. I immediately contacted customer support. They told me I had mixed funds making my winnings void. I asked for explanation and was I told I had deposited money on my account from my player rewards card when my winnings were at $600 . I said what has that to do with anything. I didn't start playing with any bonuses from casino which means I was under any bonus terms. Also if it was a problem for me to use my player rewards card to add additional funds during play why wasn't I told anything when I did it. I continued to win to about just over $1200
It's only when I tried to withdraw that they tried to find a way to deprive me of my winnings. And they Service agents were rude and refused give or show me proof that what they are saying is a rule of some sort. I read all their rules and all my player rewards card rules and they aren't any rules to support what they are claiming that using player rewards card to add money is a problem. I emailed them as well and they took long to respond and when they did they told me about reading my rules. But still no dialogue to explain or show proof of what they are claiming.
They have no problem taking money from people to play but they don't seem to want to payout when people win. They just use tactics to frustrate people in hopes they will forget about it and move on. But I want some clarity and resolve to this dispute.
It's totally unfair.

I apologize for the delay with this. This was a bit tricky, but I wanted to do whatever possible to get you a fair resolution with this...

The information you received was accurate. Throughout your play, you were mixing funds: You made a deposit, using a coupon for free spins. While playing on this same balance, you converted your bonus balance twice and then used your $50 Players Reward Card (PRC). You continued playing, redeeming more bonus balances and coupons for free spins. This is all considered 'mixing funds.'

With this in mind, I've spoken with our Finance Manager and it has been decided that we will go ahead and pay two parts of your withdrawal--$639, which was the actual build-up, based upon your cash deposit (we're removing bonuses from this) and we are also paying the max payout on your PRC. The maximum payout on the PRC is 2x the amount of the PRC deposit, so this would be $100.

Cutting to the chase, we will honor $739 of the claim.

In order to finalize this, we will need for you to confirm your Neteller details. I've sent you a PM with the email address that you'll need to send that information to.